NEW METHOD FOR DETERMINING COMPRESSIBILITY, 



With Application to Bromine, Iodine, Chloroform, Bromo- 



form, Carbon Tetrachloride, Phosphorus 



and Water. 



By Theodore William Richards and Wilfred Newsome Stull. 



Introduction. 



It has been suggested recently that since the volume of a solid or 

 liquid must be determined in part by the internal pressures to which it 

 is subjected by chemical affinity and cohesion, the compressibilities of 

 substances are probably data of important chemical significance. 1 



In attempting to interpret this significance, the enquirer at once 

 faces the fact that few pertinent compressibilities are accurately known. 

 Only complex organic compounds have been much studied, and their 

 behavior under pressure is affected by too many variables to be easily 

 interpreted. No more than four elements have been studied at all, 

 and none except mercury and copper have been investigated by more 

 than a single investigator. 



In order to fill this important gap in physicochemical knowledge, the 

 following investigation was undertaken. Its publication will be fol- 

 lowed promptly by similar more extended publications, in which the 

 compressibilities of as many elements and simple compounds as pos- 

 sible will be treated. 



The determination of compressibility is sometimes considered as one 

 of the most difficult of physical processes. The difficulty is due chiefly 

 to the fact that under pressure all the parts of any apparatus change in 

 volume, and hence the contraction under pressure of the substance 

 under examination is partly hidden. Perhaps it is this difficulty, 

 added to a lack of realization of the significance of the data, which 

 has deterred investigators from undertaking the problem more syste- 

 matically. 



Among the various methods which have been used, those involving 

 theoretical considerations of a mathematical nature, such as those com- 

 puted from the coefficient of Poisson, are of somewhat doubtful value. 



1 Richards, Proc. Am. Acad. 37, i (1901), 399 (1902) ; 38, 293 (1902). Also 

 Zeitschr. Phys. Chem. 40: 169, 597; 42: 129 (1902). 



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